In an attempt to complete my mockup of everything in front of the motor I am now looking at cooling fans. As said I already have the VA Front Runner system to bolt on the 350 Ramjet I am planning on getting in the spring. It has the upgraded 170 watt alternator.

I am somewhat limited with room as I really do not want to move the engine back.

I have just spent a considerable amount of time searching fans on this forum and on the inter-web. As usual there is lots of conflicting information.

My question is: Using the US Radiator copper 4 core high efficiency crossflow rad how many CFM's of air do I need to keep things cool?

The Flex-a Lite low profile fans that I am looking at are 2 5/8 inches thick and will fit nicely. They are rated at ca. 2500 cfm!

Is 2500 cfm going to be enough to cool the 350 Ramjet?

I live in southwestern Alberta and we might only see a few days approaching 100 degrees above and the climate is quit dry, although last summer was the exception.

Thanks in advance for again sharing your knowledge on this and the many other challenges that I am facing.

There are many theories on what's best for cooling, 4 core with a mechanical fan to 2 core with a hi performance electric. Cooling depends more on how much heat the radiator will release than CFM passing through it, CFM depends on fan capabilities and can the air get out of the fan efficiently. You look at the back of a high dollar Zirgo that claims 3000 cfm and you wonder how it could possibly pass any air at that CFM while you look at the back of a Taurus or Thunderbird fans rated at approx 2300-2500 CFM and think a hurricane could blow through these fans why is it only 2500.

What radiator type? Cross flow, the old type down flow or a split core.
Brass or aluminum. I prefer brass, The physics are better for heat transfer.

How do you want to control it?
Do you want relays or Pulse width control? can it be controlled by a PCM , If yes does the PCM have hi/lo fan options?
Prefer single fan or dual or just whatever will fit?
Do you plan on running AC?
What HP does it have?

Flex-lite would not be my first choice, OEM if you can get it to fit such as Thunderbird or Taurus or Camaro, Spal

Low profile fans are usually under 1800 cfm so i would question the 2500 rating
what ever fan you choose it needs to have 80% radiator coverage, either in a single fan or a dual or multiple fans, I ran 4 9" fans to get 4000 cfm cooling a 468 BBC here in Texas in 100 degree weather, It looked odd it was a bit loud but it worked and got by all the engine obstacles.

There are many theories on what's best for cooling, 4 core with a mechanical fan to 2 core with a hi performance electric. Cooling depends more on how much heat the radiator will release than CFM passing through it, CFM depends on fan capabilities and can the air get out of the fan efficiently. You look at the back of a high dollar Zirgo that claims 3000 cfm and you wonder how it could possibly pass any air at that CFM while you look at the back of a Taurus or Thunderbird fans rated at approx 2300-2500 CFM and think a hurricane could blow through these fans why is it only 2500.

What radiator type? Cross flow, the old type down flow or a split core.
Brass or aluminum. I prefer brass, The physics are better for heat transfer.

How do you want to control it?
Do you want relays or Pulse width control? can it be controlled by a PCM , If yes does the PCM have hi/lo fan options?
Prefer single fan or dual or just whatever will fit?
Do you plan on running AC?
What HP does it have?

Flex-lite would not be my first choice, OEM if you can get it to fit such as Thunderbird or Taurus or Camaro, Spal

Low profile fans are usually under 1800 cfm so i would question the 2500 rating
what ever fan you choose it needs to have 80% radiator coverage, either in a single fan or a dual or multiple fans, I ran 4 9" fans to get 4000 cfm cooling a 468 BBC here in Texas in 100 degree weather, It looked odd it was a bit loud but it worked and got by all the engine obstacles.

Good timing as I was just gathering some more information to present my case so hopefully forum members might be able to see better what I am trying to do.

The truck is a 1956 Task Force that I have sitting on a shortened 1980 1/2 ton frame. I am planning on a 350 Ramjet that is rated at 350 horse and 400 foot pounds.

My radiator is a US Radiator copper/brass crossflow with what they call an 80's style core with 1/2 inch tubes on 3/8 inch centres and is a 4 row which makes it 2 5/8 inchs thick. The core measures 24 1/2 X 17 1/2.

The radiator does not have the automatic trany cooling function so will be cooled by a remote trany cooler that I have purchased on the advice of my trany rebuilder guy- a reputable shop in a nearby city.

The fan I am looking at, so far mainly because it will fit, is a Flex-a-lite dual 12 1/8 Lo-Profile s-blade with variable speed controller. It measures 26.25 X 15.5 inches and is 2 5/8 inches thick. It is rated at 2500 cfm.

Yes I will have AC.

As said the dual fans I am looking at are controlled by a variable speed controller but I am certainly open to all suggestions.

Not sure if I answered all your very good questions so feel free to fire back. Being a builder from Texas I am sure you have lots of knowledge on all things related to cooling our trucks. I really appreciate your response.

I am also open to your suggestions as I have not ordered the fans yet. I will look at Spall.

There is also a slight chance that I could gain another inch by getting some Dirty Dingo engine mount sliders but would have to put my cab back on the frame and see how much room I have. I really do not want to have to cut into the firewall to create more room. I still have the mock up engine and 700r4 trany sitting in the frame. That extra inch might allow me to go with fans that are thicker and have higher cfm ratings.

congrats on the ramjet 350, best part i ever bolted into truk, a little pricey but well worth it
every spring i turn the key and it starts right up after sitting all winter

you should have lots of room for any fan/radiator setup
i have 3'' or 4'' between the fan and water pump

can't help you with part numbers, i have a stock looking us radiator 4 row desert cooler with trans cooler built in
i bought the us radiator shroud with 16'' spal puller fan from us radiator
having the shroud to cover most of the core is very important, wire tying a fan to the rad is not good for air flow

i used the running sbc that came in truk to mock up motor/trans mounts
i had to modify the firewall a tad due to the huge plug coming off the back of the distributor on the ramjet 350
also modified the mefi controller and coil brackets from the back of the motor to over the valve covers

Thanks for your response. I have absolutely no room for a pusher as I have the trany cooler mounted up front.

At 350 hp you can use a 2500 and should not have any issues

I don't know about their control, if its variable then it's most likely a pulse width modulated unit but you can google flex-a-lite pwm problems or flex-a-lite variable control problems and see what pops up. All units have some issues no matter who's making them so if it's only a few then it's most likely an ok unit. Most issues with PWM units is the installer or the buyer trying to drive a fan that over its capacity, ie a 40 amp PWM trying to drive a Mark 8 fan. or the installer connecting it up backwards

With relays controls we typically control the hot side of the circuit, with PWM we control the ground side so for those of us that don't read instruction we hook it up backwards and cook the circuitry and blame the control.

Pros to PWM are sped rams up as needed making the fan quieter in most cases. depending on how and where their reading the temp, usually at the lower rad outlet return, it only runs when the radiator is hot so if you're on the highway the rad is cool the fan will not come on. They are adjustable to your normal temp providing you have a Tstat lower that the temp you want to run.

Cons are they some time have a low speed clicking or buzzing, starting the fan below 50%, spal and flex-a-lite eliminate this by starting the fan at 60% power. They are often time more expensive and not as reliable as a good old really. They are sensitive to other PWM devices in the car and can cause disturbances between the units unless you shield them.

Pros for relays. you can get a replacement at any parts house. Time tested part, usually very inexpensive.

Cons, the fan or device is either on or off no inbetween. The temp sensors are usually in the block or Tstat housing so it the engine is at say 185F the fan comes on whether you at highway speed or not.

i used the running sbc that came in truk to mock up motor/trans mounts
i had to modify the firewall a tad due to the huge plug coming off the back of the distributor on the ramjet 350
also modified the mefi controller and coil brackets from the back of the motor to over the valve covers

Ogre thanks for your response. I actually don't have the ramjet engine yet but am trying to do the final mockups before I head south for a few months this winter. But if all goes well I will have it ordered and sitting at the dealer waiting for me when I get back.

I have been doing my mockup with a 283 with its stock distributor. I am most interested in what you have said regarding the"huge plug coming off the back of the distributor" and your "modification of the mefi controller and coil brackets."

I am thinking that I need to put the cab back on the frame to see how much room I have back there and if I will need to do the same. Modifying the firewall has always scared me but I like the looks of yours!

Do you have any idea of how much farther the "huge plug" sticks out as compared to the stock distributor?

Also did you have to modify the mefi controller and coil brackets because of space available back there or because you just wanted to move?

I don't know about their control, if its variable then it's most likely a pulse width modulated unit but you can google flex-a-lite pwm problems or flex-a-lite variable control problems and see what pops up. All units have some issues no matter who's making them so if it's only a few then it's most likely an ok unit. Most issues with PWM units is the installer or the buyer trying to drive a fan that over its capacity, ie a 40 amp PWM trying to drive a Mark 8 fan. or the installer connecting it up backwards

With relays controls we typically control the hot side of the circuit, with PWM we control the ground side so for those of us that don't read instruction we hook it up backwards and cook the circuitry and blame the control.

Pros to PWM are sped rams up as needed making the fan quieter in most cases. depending on how and where their reading the temp, usually at the lower rad outlet return, it only runs when the radiator is hot so if you're on the highway the rad is cool the fan will not come on. They are adjustable to your normal temp providing you have a Tstat lower that the temp you want to run.

Cons are they some time have a low speed clicking or buzzing, starting the fan below 50%, spal and flex-a-lite eliminate this by starting the fan at 60% power. They are often time more expensive and not as reliable as a good old really. They are sensitive to other PWM devices in the car and can cause disturbances between the units unless you shield them.

Pros for relays. you can get a replacement at any parts house. Time tested part, usually very inexpensive.

Cons, the fan or device is either on or off no inbetween. The temp sensors are usually in the block or Tstat housing so it the engine is at say 185F the fan comes on whether you at highway speed or not.

Hey this is good news on the 2500 cfm front!

Flex-a-lite also lists an adjustable thermostatic controller! Is that any better than the variable speed controller? Or are they two different things. As you can tell I know nothing about this sort of stuff.

It looks like there may be options for controlling whatever fans I get and I really don't have to make any decisions on that front yet although it is good to plan ahead.

Up until a few years ago I never even had AC in my personal vehicles!!! My wife has for ever but my old trucks never...

56, I got the dual 11" inch SPAL puller fans w/aluminum shroud for my aluminum U.S. Radiator cross flow in the 57. Haven't run it yet, but Jim at U.S. Rad said it should be plenty to keep my 383 Stroker cool. I believe they only extend around 2.5" from radiator.

Flex-a-lite also lists an adjustable thermostatic controller! Is that any better than the variable speed controller? Or are they two different things. As you can tell I know nothing about this sort of stuff.

It looks like there may be options for controlling whatever fans I get and I really don't have to make any decisions on that front yet although it is good to plan ahead.

Up until a few years ago I never even had AC in my personal vehicles!!! My wife has for ever but my old trucks never...

Adjustable means that you can adjust the temp it starts the fan at. its an On/off device like a relay. variable mean the fan starts at 60% power and spins the fan at say 1000 rpm if it needs more cooling it spins it up to say 1800 rpm , less cooling it ramps it down again.

Some of the adjustables have a big probe you push into the radiator fins to pick up the temp. It's a better place to read temperatures but the device is a hot water heater thermostat somebody figured out could be used for cars.

There are digital adjustables but again it's an ON OFF device.

Ac makes a difference. You want the fan to come on full speed when the compressor engages so you don't pop a compressor head due to pressure build up and excess heat.

56, I got the dual 11" inch SPAL puller fans w/aluminum shroud for my aluminum U.S. Radiator cross flow in the 57. Haven't run it yet, but Jim at U.S. Rad said it should be plenty to keep my 383 Stroker cool. I believe they only extend around 2.5" from radiator.

Cheers, Jim

Hey Jim

I really like the clean look of that dual fan set up. I have recently emailed a fellow from US Radiator and he said that they custom make fan/shroud combos and your rad is pretty much identical to mine except aluminum. I bet they could make me one on spec!

Is there any chance you could get an exact measurement out from the rad fins?

If its only 2 1/2 it would easily work for me also. I have closer to 3 inches of real estate available in there!!!

How does it attach to the radiator?

Also is there a number on the fan motors? I would like to see what they are rated at and what they pushing out for cfm.

I am now feeling pretty darn good about 2500 cfm fans on my system especially if yours is also in that ballpark. The Spal fans have a real good reputation! If I am reading the inter-web reviews I have been seeing probably even better than Flex-a-lites I have been looking at.

Anyway thanks a ton. I look forward to seeing how the shroud attaches and exactly how wide it is.

I really like the clean look of that dual fan set up. I have recently emailed a fellow from US Radiator and he said that they custom make fan/shroud combos and your rad is pretty much identical to mine except aluminum. I bet they could make me one on spec!

Is there any chance you could get an exact measurement out from the rad fins?

If its only 2 1/2 it would easily work for me also. I have closer to 3 inches of real estate available in there!!!

How does it attach to the radiator?

Also is there a number on the fan motors? I would like to see what they are rated at and what they pushing out for cfm.

I am now feeling pretty darn good about 2500 cfm fans on my system especially if yours is also in that ballpark. The Spal fans have a real good reputation! If I am reading the inter-web reviews I have been seeing probably even better than Flex-a-lites I have been looking at.

Anyway thanks a ton. I look forward to seeing how the shroud attaches and exactly how wide it is.

Ogre thanks for your response. I actually don't have the ramjet engine yet but am trying to do the final mockups before I head south for a few months this winter. But if all goes well I will have it ordered and sitting at the dealer waiting for me when I get back.

I have been doing my mockup with a 283 with its stock distributor. I am most interested in what you have said regarding the"huge plug coming off the back of the distributor" and your "modification of the mefi controller and coil brackets."

I am thinking that I need to put the cab back on the frame to see how much room I have back there and if I will need to do the same. Modifying the firewall has always scared me but I like the looks of yours!

Do you have any idea of how much farther the "huge plug" sticks out as compared to the stock distributor?

Also did you have to modify the mefi controller and coil brackets because of space available back there or because you just wanted to move?

this is the best pic i could find on line of the ramjet 350 plug. this is in a tri5 chevy, he was able to index the distributor to make it work. i tried indexing mine to the side and hit the firewall. this is the plug plus you have the female end and wires. sticks out 2 inches from what i recall. my firewall mod could have been smaller, the distributor is not an issue only the plug.

the mefi controller and coil brackets are designed to mount on the back of the each head. doesn't work on our trucks.

yeah you need to throw the cab on to check the fit. both fuel lines exit on back near the same area too. you can see the supply line up front and the return regulator behind the distributor in this pic. i had the stock front motor mounts on the sbc when i fabbed the motor and trans mounts. my motor is in the stock location for a v8.

if you winter anywhere near sarasota fl, look me up. i'll be heading down after xmas
heading south for you could be kalispell montana

56, looks like the fans stick off of the shroud 2 1/8" and the shroud may be another 1/4" off the radiator - so less than 2 1/2" total thickness. The shroud is bolted across the top and bottom of radiator. Fans are Spal VA09-AP8's.

56, looks like the fans stick off of the shroud 2 1/8" and the shroud may be another 1/4" off the radiator - so less than 2 1/2" total thickness. The shroud is bolted across the top and bottom of radiator. Fans are Spal VA09-AP8's.

I have been doing a ton of research, basically because winter has hit us so not much else to do.

I go out to the shop and work on different things and then come back in and research what I am currently doing, what I want to be doing next and it goes on and on...

I have changed my mind about 10 times on my shroud and fan set up!!!

So what I am thinking now is I want to go with a shroud like yours from US Radiator but would like to put 2 - 12 inch fans for a few more cfm's. I have a fellow from US Radiator looking into if there is room on that shroud to mount the 2 offset/staggered 12 inch fans. If there is enough room they will build me a shroud and hopefully mount the 2 fans I have identified.

Part of my problem is the fact that I have my 56 body sitting on a 1980 1/2 ton frame. So it changes a few things and limits my options.

I would probably be okay with the 2-11 inch fans but if I can kick them up to 2 12 inch fans I am going to!

Probably have to wait till Monday now to hear back from US Radiator now.

this is the best pic i could find on line of the ramjet 350 plug. this is in a tri5 chevy, he was able to index the distributor to make it work. i tried indexing mine to the side and hit the firewall. this is the plug plus you have the female end and wires. sticks out 2 inches from what i recall. my firewall mod could have been smaller, the distributor is not an issue only the plug.

the mefi controller and coil brackets are designed to mount on the back of the each head. doesn't work on our trucks.

yeah you need to throw the cab on to check the fit. both fuel lines exit on back near the same area too. you can see the supply line up front and the return regulator behind the distributor in this pic. i had the stock front motor mounts on the sbc when i fabbed the motor and trans mounts. my motor is in the stock location for a v8.

if you winter anywhere near sarasota fl, look me up. i'll be heading down after xmas
heading south for you could be kalispell montana

I have just today turned the cab back on its nose so I can finish the underside of the floorboards. Little more welding then some fibreglass reinforced bondo over my welds then epoxy primer, seam seal and undercoating. Hope to have it back sitting on the frame before I go south after Christmas.

Again the 56 body sitting on the 80 1/2 tone frame present a few new challenges.

I never knew about the plug on the distributor until you mentioned it and thought I was going to be okay after my original mockup.

I also never knew where the Mefi was sitting and know it also not work for me not he back of the head.

Cant wait to get the cab sitting back on the frame to tackle those little issues.

Your right Kalispell is just a hop, skip and a jump from where I live in the southwestern corner of Alberta but we winter in Arizona.

This is really good stuff. Thank you so much for directing me to this. The preferred method diagram you sent is not coming through very well. Maybe I just have to wait and it is my slow internet. I am out in the country and suffer from slow internet speeds. No matter which way I go I will be using this. It incorporates everything my research has turned up.

I have narrowed it down to two choices now.

The one is dependent on wether US Radiator can fit two Spal 12 inch fans (Summit #30101522 @ 2.44 inches thick and 1328 cfm on a single fan for ca. 2650 cfm for both) on their fan shroud that is designed for my radiator. It is a really compact clean shroud that only sticks out 1/2 inch.

The other fan set up comes mounted on a shroud. It is the Flex-a-lite Low profile (Summit # Flex-a-lite 420) and is 2.625 inches thick and puts out 2500 cfm. Their shroud, that is black plastic does not perfectly fit my radiator but is workable.

My issues arise out of the fact that i have put a 56 body on a 80 1/2 ton frame. The frame is not flat which creates issues and of course the space that I have available i.e. ca. 3 inches.

Another shroud and fan set up that I really like is the Derale 26 inch high output. This one looks a lot like what you made with the flaps for increased high speed air flow. It is about 3.5 inches thick and puts out 4000 cfm. The shroud will however require some modification due to its 26 inch width.

Hopefully US Radiator will get back to me on Monday with good news and they can fit those fans on their shroud. The Spal web site has a great schematic on this fan so I am sure their people will be able to figure out wether there is enough room.

So I finally made a decision after lots of research and several emails with Jim Allen at US Radiator. I bought the radiator from them. Jim by the way is great to deal with. He showed much patience with me and really helped me figure this out.

I have purchased 2 -12 inch Spal fans from Summit pushing out ca.1350 cfm each and are only 2.44 inches thick. They are on their way to US Radiator as we speak. This should with the ca. 1/2 inch shroud keep me at about 3 inches in overal width. This is what I was shooting for all along!

Jim has agreed to increase the width of the stock shroud by 1 inch to allow the two 12 inch fans to be mounted in it. I will need to slightly modify it to allow fitment for the inlet and outlet hoses. This will be minimal, somewhere around 3/8 of an inch on each side just around the hoses. Probably have to do small notch for the drain as well. This of course will mean I cannot return it but that's okay by me.

This whole process was also greatly aided by our forum members.

I may have been okay with the 11 inch fans in the stock shroud but with air conditioning and a 4 row radiator that is 3 inchs thick really felt that I needed the extra cfm.

Anyway thanks all who contributed. Once I have it all mounted I will post pictures for sure.